Means for connecting a calculator with a printer or other recording means



R. J. LA MANNA MEANS FOR CONNECTING A CALCULATOR WITH April 23, 1957 A PRINTER OR OTHER RECORDING MEANS 2 Sheets-Sheet 1 Filed D60. 30, 1953 Q fi 1055 0255.5

INVENTOR RICHARD J. LAMANNA o 0 a c n QOZUJOW OZELuhW h ON PTML .rZEm

AGENI Apnl 23, 1957 R. J. LA MANNA MEANS FOR CONNECTING A CALCULATOR WITH A PRINTER oR OTHER RECORDING MEANS 2 Sheets-Sheet 2 Filed Dec. 30, 1953 INVENTOR Fl CHARD J. LAMANNA United States Patent MEANS FOR CONNECTING A CALCULATOR PRINTER OR OTHER RECORDING Richard J. Lu Manna, Morristown, N. J., assignor to Monroe Calculating Machine Company, Orange, N. J., a corporation of Delaware Application December 30, 1953, Serial No. 401,310

17 Claims. (Cl. 235-604) This invention relates to means for controlling printing or other display means differentially in accordance with the results of computations performed on a calculating machine or the like.

Many calculating machines and the like are known which do not include means for printing the results of computations performed thereon but rather, display the results on one or more indicator dials. These machines are extremely useful and highly efiicient where no printing or other permanent record of the results of the calculations performed thereon is required. However, where a permanent record is required it becomes necessary for a typist, or the like, to read the indicator dials and then type or otherwise record the number displayed thereby, an operation which is not only time consuming but which also increases the possibility of a human error entering into the system. To overcome this deficiency, it has been proposed to connect printing or other recording means to such machines to print or otherwise record the numbers displayed on the indicator dials.

In certain known calculating machines the indicator dials which display the results of computations performed thereon and the dilferentially operable actuators for said dials are so embedded in mazes of mechanism that it is extremely difficult, if not impossible, to mechanically connect printing or other recording means thereto. The difficulty involved in making such connections is further increased by the requirements that they be made without resorting to the expedients of defacing the dials or blocking visual access thereto. Still further, it has been found that in some machines the dial actuating means or the means for controlling the same are of such delicate nature that additional mechanical loads cannot be safely placed thereon.

The principal object of the invention, therefore, is the provision of means for controlling printing or other display means differentially in accordance with the results of computations performed on a calculating machine, or the like, which means are free of the objectionable qualities set forth above.

In the known calculating machines one set of dials is provided for displaying quotients and another set is provided to display products. The product dials in such machines are set differentially under control of a plurality of actuators which operate more or less simultaneously. The quotient dials, however, are set differentially by a single actuating means which cooperates with the dials seriatim.

in general, the quotient dial actuating means advances the dial with which it is associated, one digital place or step on each operation thereof. Therefore, the setting of each dial to represent a quotient digit, is the result of a series of successive operations of the actuating means. According to the invention, means .settabl'e or operable differentially in conjunction with the setting of each quotient dial are provided to effect recording the digits displayed by the dials through the medium of a serially operable printer or recording device, for example, a typehi writer. This arrangement provides not only for the recording of quotients computed on the calculater, but also the results of all other calculator operations which may be transformed into quotients merely by dividing the same by one.

In some of the known calculators, division operations are performed in accordance with the so-called subtract, add, shift program. According to this program, each dividend is entered into a register in the calculator car riage, while each divisor is entered into a set of differential actuator gears Which coact with the said register in such wise that on each of a plurality of successive cycles the divisor is subtracted from the dividend and its remainders until an overdraft is created. Then, the actuator gears are operated in reverse to add the divisor to the ovcrdrawn remainder, after which, the calculator carriage is shifted leftward one denominational order, and the program repeated. Meanwhile, a quotient dial is advanced one digital position on each subtraction cycle including that on which the overdraft is created, and then restored one step during the add or overdraft correction cycle to display the true quotient digit.

According to one form of the invention, means are provided which count the subtraction cycles and, on the occurrence of the add or correction cycle effect printing of the digit which is one less than the number counted.

in others of the known calculators, division operations are performed in accordance with a variable program (subtract, add, shift, or subtract, shift). In this type machine, each divisor is subtracted from the associated dividend and its remainders on each of a plurality of successive cycles until comparison means tentatively determine that the divisor is larger than the remainder, at which time the machine is stopped and a second comparison made to determine whether or not the machine was stopped in time to prevent an overdraft. If no over draft occurred, the carriage is shifted one denominational order leftward, and the process repeated. However, if an overdraft did occur, then the divisor is added back to the overdrawn remainder before the carriage is shifted. Here again, the number of subtraction cycles ind cates the value of each quotient digit, although in some instances the number of such cycles may be one greater than the value of said digit, while in other instances it is equal thereto. According to another form of the invention, means are provided which count the said subtraction cycles and effect printing of the digit which is one less than the number counted, or said number itself, depending on whether or not an overdraft occurred.

The invention contemplates that the means for counting the subtraction cycles may also count the add or correction cycles and/ or any other cycles entering into a particular division program and still be able to effect printing of the appropriate digits.

The invention also provides means whereby tabulate operations of the printer may be effected and also other means for effecting other desired printer operations.

In a preferred embodiment of the invention the same is used to effect operation of the print control solenoids of a typewriter selectively under control of a calculator which performs division in accordance with the subtractadd-shift program. Preferably, the means of the inven-- tion include a stepping switch having contacts appropriate to the digits 0-9 connected to the print solenoids to effect energization thereof selectively, switching means controlled by a timely operable calculator member to block energization of the print solenoids except on overdraft correction (add) cycles of the calculator, means actuated by a timely operable member of the calculator to advance the stepping switch one step during, each subtraction cycle of a division operation, and means actuated by a timely operable member of the calculator to home the stepping switch duringeach shift cycle of a division operation, the switch being horned to the 9 contacts to compensate for the advances thereof made on overdraft producing subtraction cycles.

Other objects and advantages of the invention will become apparent when viewed in the light of the drawings of which:

Fig. l is a schematic wiring diagram showing the means of the invention; Fig. 2 is a portion of Fig. 7 of U. S. Patent 2,531,207 and illustrates the manner in which the means of the present invention are applied to a calculator of the type disclosed in said patent; and.

, Fig. 3 is a portion of Fig. 24 of the above entitled patent and further illustrates the manner in which the means of the present invention are applied to the calculator of. the patent.

Before entering into a detailed description of the means of the invention, it is deemed advisable first to describe briefly the means whereby the calculator disclosed in the above cited patent is adapted for use with the means of the invention. Referring to Fig. 2 a micro-switch 32 is secured to the righthand sideplate ol' the calculator with. its armature in position to cooperate with a cam 31 fixed on drive shaft 350 of the machine. A rotation of this shaft 350 measures a registration (add or subtract) cycle of the calculator. Therefore, the switch 32 is operated once per registration cycle.

Referring now to Fig. 3, a pair of micro-switches 33 and. 35 are secured to the lefthand frameplate of the calculator with their armatures in position to cooperate with machine elements 34 and 658', respectively. Element 34 is a stud-like extension of the pivot-connection between arm 732 and link 733 of the calculator which is rocked clockwise with said arm on initiation of a division operation of the calculator and remains so rocked for the dura tion of the said operation. Thus switch 33 is held operated by the stud 34 all during division operations. Element 658 which controls Switch 35, comprises a lug or car projecting laterally from the end of slide 658, which is maintained in its forward (rightward in the drawing) position, all during subtraction cycles of a division opera tion, but is moved rearwardly to initiate the add or correction cycle following each overdraft producing subtraction cycle. Slide 658 is retained in its rearward position for approximately one-half cycle, after which it is restored to its normal forward position. The cooperation between lug 658' and switch 35 is such that the switch remains in its normal condition while the slide is in its forward position, but is operated when the slide moves rearwardly.

Reference is made to the aforecited patent for more detailed descriptions of the shaft 350 and the members 658 and 732. It is to be mentioned that, if desired, shaft 4 of the calculator which rotates at the same rate as shaft 350, or any other timely operable machine element, may be used to control micro-switch 32, and in like manner, other timely operable machine members may be substituted for slide 658 and its lug 658 or arm 732, etc.

Referring to Fig. l, the means of the invention include a stepping switch 43 having three banks of contacts A, B, and C. Contact bank A includes ten contacts appropriate to the digits -9, each connected via a conductor 44 with the appropriate digit printing control solenoid 45 in an electric typewriter 46. The solenoids 45 are also connected to ground by means of a common conductor 47 and contacts 37 of micro-switch 35 which are closed only when the slide 658 is moved rearwardly during the correction cycle which follows each overdraft producing subtraction cycle of the calculator. Evidently, therefore, the. solenoids are operable only during the correction cycles of the calculator. Selection of the solenoid to be operated on each said correction cycle is accomplished by. the wiper 48 for the contacts of bank A. To this end wiper. 48,, which in its home or normal position, is'engaged withthe 9 contact of the bank but which is advanced at least to the zero contact during the calculation of each quotient digit, is connected via a conductor 49 with a positive bus 42. This bus, in turn, is connected with a suitable source of electric power through contacts 38 of the micro-switch 33, which are closed for the duration of each division operation of the calculator, and a Print switch 41 which is closed only when it is desired to print the results of computations performed on the calculator.

Bank C of stepping switch 43 includes a single wired contact which is engaged by a wiper 63 when the wiper t; of A engages contact 9 of the latter bank, that is, in. me home or normal position of the switch. This single contact of bank C is connected to the positive bus 42 and the wiper 63 serves to connect the same with a conductor 64 which, in turn, is connected to a relay 60. The circuit for said relay is completed to ground over a conductor 71 and through contacts 36 of micro-switch which are closed except when slide 658 moves rearwardly during correction cycles. A holding circuit for said relay provided through a lead 65 and contacts 62 thereof.

It is believed evident that following closure of the Print switch 4!. and operation of arm 732 of the calculator i to close contacts 38, the relay 60 is energized and remains energized until the contacts 36 are opened on rearward movement of the slide 658 during the next following correction cycle.

Bank B of the stepping switch is provided with intcrconnected contacts in positions to be engaged by a wiper Su e/hen the wiper 48 for bank A. is in engagement with any of the contacts 0-8. No wired contact is provided at the 9 position.

The wipers 48, 50 and 63 are advanced in unison by means of a stepping solenoid 51 which is connected to the positive bus 42 and also via a conductor to the switch 32 which extends the connection to ground when it is closed by a cam 31.- Evidently, therefore, stepping solenoid 5.1 energized to advance the wipers one step during each registration cycle of the calculator.

In order to home the wipers 48, 50 and 63 from whatever positions 08 they have been advanced to during registration cycles of the calculator, the negative terminal of solenoid 51 is connected through interrupter contacts 52 thereof with the wiper 50 of bank B of the switch. Said wiper 50, in turn, extends the connection through the interconnected contacts of bank E, a conductor 53, back contacts 61 of relay 6!) and the conductor '71 to the contacts 36 of: micro-switch 35. During subtraction cycles, the contacts 61 are held open by the energized relay 60. However, when the slide 653 moves rearwardly on each correction cycle and effects deenergization of relay 66, the contacts 61 close, so that when the slide 658 is restored to its normal position and the contacts 36 are reclosed thereby, a path to ground for the stepping solenoid 51 is provided. In well known manner, the interrupter con tacts 52 effect repeated'operations of the solenoid which advances the wipers 48, 50 and 63 to their home or 9" positions. When wiper 50 reaches the unwired 9 position of contact bank 8 the path to ground for the stepping solenoid is opened and the same becomes deenergized. At the same time advance of ,wiper 63 to the 9" position of bank C efiects reenergization of relay 60.

At this point it is deemed desirable to describe the operation of the means of the invention in connection with a simple division operation. It will be assumed by way of example, that a dividend of 96 has been entered this condition while the calculator cycles through four subtraction operations, in each of which, the divisor 3 is subtracted from the tens order dividend digit 9 and its remainders. On each subtraction cycle the stepping switch wipers 48;, 50 and 63 are advanced one step under control of cam 31 and switch 32. Therefore, said wipers are advanced to their 3 positions from their home or 9 positions. The fourth subtraction cycle, of course, produces an overdraft, and the slide 658 is moved rearwardly to initiate a correction (add) cycle. This movement of the slide closes the contacts 37 and a path to ground is provided for the 3 print solenoid 45 which is also connected to the positive bus 42 through the wiper 48 of: bank A of the stepping switch. Therefore, said 3 solenoid is energized and the digit 3 is printed.

Rearward movement of the slide 658 also effects deenergization of the relay 6i and when. said slide is restored to its forward position and the contacts 36 closed thereby, the homing circuit for the stepping switch is completed and stepping solenoid 51 is energized to home the wipers 48, 5t and 63 to their 9 positions.

On homing of the stepping switch, the relay 69 is reenergized, and, following the correction cycle, the calculator operates to effect a carriage shift operation as de scribed in the aforecited Gang patent. The shaft 356 is not rotated during carriage shifting operations and thus the stepping switch is not elfected thereby during such operations.

Following the carriage shift operation, the calculator operates to subtract the divisor 3 from the units order dividend digit and its remainders on each of three suc cessive cycles, of which the last produces an overdraft. During these three cycles the stepping switch 43 is advanced from its 9 position to its 2 position in which the wiper 48 thereof connects the solenoid d5 of the typewriter with the positive bus 42. On initiation of the correction cycle following the overdraft producing subtraction cycle, the contacts 37 are closed as described above and the said 2 solenoid is energized to print the quotient digit 2. At the same time the contacts 36 are opened to deenergize the relay no. Therefore, when during the correction cycle the slide 656 is restored to normal and reclo-ses said contacts 36, another homing operation of the stepping switch is effected. Following computations of the lowest order quotient digit, in the present instance the digit 2, the arm 732 of the calculator is rocked counterclockwise (Figs. 1 and '3) in the manner described in the af'orecit'ed patent to Gang and disconnects the positive bus 42 from the source 20 of electrical power. Therefore, the means of the invention are disabled until the next division operation of the calculator is initiated and the arm is rocked clockwise again.

It will be seen, therefore, that the correct quotient of theproposed problem 96:-3, namely 32, has been printed. It is to be mentioned that where the results of computations other than division are to be printed, such results are substituted for the dividend in the above recited problem and a divisor of 1 is entered into the machine so that the resulting quotient is equal to the said dividend.

In order to tabulate the carriage of typewriter 46 preparatory to printing each quotient computed by the calculator, the usual tabulate control solenoid 85 for the type writer is connected between ground and a pair of contacts 82 of a relay 81 (Fig. 1). Contacts 82 are normally open but on energization of the relay are closed to connect the tabulate solenoid 85 to the source of electrical power 20. Evidently when this last connection is made the tabulate solenoid 85 is energized and effects a tabulate operation of the typewriter in the usual manner.

Relay 81 is controlled by arm 732 of the calculator in such wise that the relay is energized each time said arm rocks counterclockwise in the drawing to signify the completion of a division operation of the calculator. To this end, the coil of relay 8]. is connected between ground and the contacts 39 of the switch 33 which are closed on counterclockwise movement of the arm, 732, and remain closed until initiation of a later division operation. Closure of these contacts connects the coil of relay 81 to the source 20 of electrical power, and in order to produce only a momentary energization of the relay 81, sufiicient in duration to effect energization of the 'tabulate solenoid 85, a condenser 79 is interposed in the connection between the coil of the relay and the contacts 39. A resistor is connected between the positive terminal of condenser 79 and ground. A judicious selection of values for condenser 79 and resistor 80 provides a time constant sufficiently long so that on closure of the contacts 39, energizing current flows through the coil of relay 31 for the desired length of time. The relay, of course, becomes deenergiz-ed as soon as the condenser '79 is fully charged. it will be noted that resistor 80 also provides a discharge path to ground for condenser 79 when the contacts 39 are opened on initiation of each division operation.

In some instances, it may be desired to effect line spacing operations of the typewriter rather than tabulate operations, between successive quotient printing operations. To this end the typewriter line spacing control means may be substituted for the tabulate solenoid in the circuit of Fig. 1.

At this point it is to be mentioned that the controls effected by the arm 732 of the micro-switch 33 in the circuit of Fig. '1 could be effected by a modified print switch 41. Ina circuit arranged in this way, however, it is necessary for the operator of the calculator to manipulate the print switch before and after each division operation of the calculator.

Whereas the invention has been described in connection with a calculator of the type disclosed in U. S. Patent 2,531,207 to Herman Gang, it is equally well adapted for use in connection with other types of calculator, for example, the type of calculator disclosed in U. S. Patent 2,229,889 to Carl M. Friden. In applying the means of the invention to the Friden calculator, parts 321, 592 and 586 thereof may be used to ellect appropriate operation of the micro-switches 32, 33 and 35 of the means of the invention, or their equivalents, instead of cam 31, arm 732 and slide 658, respectively, as described above in connection with the Gang calculator. Reference is made to Figs. 1C, 6, 7, 8 and 18 of the Friden patent for illustrations of parts 321, 592 and 586. Briefly part 321 is a shaft which is shifted axially during each subtraction cycle and therefore can be used in much the same way as cam 31. Part 592 is an arm of a bell crank 594 which is rocked clockwise to initiate a division operation and is maintained in its rocked position for the duration of such operation, much the same as arm 732 of the Gang calculator; and finally part 586 is an arm which is rocked clockwise to initiate each correction cycle of a division program and thus may be used in the same manner as the slide 658 described hereinabove. It is to be understood, of course, that other timely operable elements of the Friden calculator may be substituted for those mentioned above.

The means of the invention are also applicable to calculators of the type disclosed in U. 5. Patent 2,2ll,736 to Harold T. Avery which perform division in accordance with a variable program of operation (subtract, shift or subtract, add, shift). In calculators of this type the number of subtraction cycles which are involved in the computation of each quotient digit is not always greater by one than the quotient digit, as is the case in the Gang and Friden calculators, but only when the comparison mechanism of the machine fails to avert an overdraft. Whenever an overdraft is averted the norm ber' of subtraction cycles is equal to the quotient digit. Therefore, the means of the invention as applied to calculators of this type include provisions for effecting a one step advance of the stepping switch. not only in response to each subtraction cycle of the calculator, but also whenever an overdraft is averted by the calculator comparison mechanism. Thus, the number of steps of advance of the stepping switch is always greater by one than the quotient digit to be printed, the same as described above in connection with the Gang and Friden machines.

The means of the invention may be applied to the Avery calculator as follows: Switch 32 of Fig. 1 may be operated once per subtraction cycle by a suitable cam mounted on shaft 166 (Figs. 1 and l014 of Avery). It is to be noted that shaft 166 rotates at half speed so that a cam having two diametrically opposite lobes would have to be provided in place of the single lobed cam 3.1 shown in Fig. 1. In addition, another switch similar to the switch 32 of Figs. 1 and 2, connected electrically in parallel with switch 32 but adapted to advance the stepping switch one step whenever an overdraft is averted, may be mounted for operation by interponent 612 (Fig. 42 of Avery) I when the same has been rocked counter-clockwise about itsv pivot 518 by bell crank 2073 and then is further. rocked counterclockwise along with lever 519 about shaft 501 under control of cam 517. Switch 35 may be operated by member 1377 (Figs. 42 and 89 of Avery) which is moved in unique manner to initiate a carriage shift operation of the calculator following computation of each quotient digit. Preferrably switch 33 (Fig. 1) is eliminated and a suitable manually operable print switch 41 substituted therefor.

Reference is made to the Avery patent for a more detailed description of shaft 166, interponent 612, cam 517 and member 1377 and other timely operable machine elements which may be substituted therefor.

While there have been above described but a limited number of embodiments of the invention, it is to be understood that many changes and additions may be made in the means thereof without departing from the spirit of the invention and it is not desired, therefore, to limit the scope of the invention except as pointed out in the appended claims or as dictated by the prior art.

1 claim:

1. Means to effect operation of the print control solenoids of a typewriter selectively under control of. a calculator which performs division in accordance with the subtract-add-shift program comprising a stepping switch having contacts appropriate to the digits 0-9 connected to the print solenoids to effect energization thereof selectively, switching means controlled by a timed operable calculator member to block energization of the print solenoids except on overdraft correction (add) cycles of the calculator, means actuated by a timed operable member of the calculator to advance the stepping switch one step during each subtraction cycle of a division operation, and

.means actuated by a timed operable member of the calculator to home the stepping switch during each shift cycle of a division operation, the switch being horned to the 9 contacts to compensate for the advances thereof made on overdraft producing subtraction cycles.

2. Means to effect operation of the print control solenoids of a typewriter selectively, under control of a calculator which performs division in accordance with the subtract, add, shift program comprising a stepping switch having contacts appropriate to the digits 0-9 connected to the print. control solenoids to effect energization thereof selectively, a first switching means operable to block energization of the print control solenoids excent on overdraft correction, add cycles of the calculator, a second switching means operable to advance the stepping switch one step during each subtraction cycle of a division operation of the calculator, a third switching means operable to home the stepping switch during each .shift cycle of a division operation of the calculator,

the stepping switch being arranged to home the contacts appropriate to the digit 9 to compensate for advances thereof made on overdraft producing subtraction cycles,

.and' timed operable calculator elements for operating the first, second and third switching means.

3. The combination with a calculating machine which performs division in accordance with the subtract, add,

8 shift program and which includes a first member operablc in conjunction with each subtraction cycle of a division operation, a second member operable in conjunction with each overdraft correction, add cycle, and a typewriter in cluding a print control solenoid for each digit 0-9; of a stepping switch having contacts appropriate to the digits O9 connected to said print solenoids to effect energization thereof selectively, switching means operated by said second member to block energization of the print control solenoids except on overdraft correction, add cycles of the calculator, switching means operated by said first member to advance the stepping switch one step for each subtraction cycle of a division operation, and means under control of the calculator to home the stepping switch in conjunction with each shift cycle of a division operation, the stepping switch being homed to the contacts appropriate to the digit 9 to compensate for the advances thereof made in conjunction with overdraft producing subtraction cycles.

4. The combination with a calculating machine which performs division in accordance with the subtract, add,

shift program and which includes a first member operaole in conjunction with each subtraction cycle of a division operation, a second member operable in conlator, switching means operated by said first member to advance the stepping switch one step for each subtraction cycle of a division operation, and means under control of the calculator to home the stepping switch in conjunction with each shift cycle of a division operation, the stepping switch being horned to the contacts appropriate to the digit 9 to compensate for the advances thereof made in conjunction with overdraft producing subtraction cycles.

5. The combination with a calculator adapted to perform division by means of repeated subtraction and a recorder including record control solenoids appropriate to the digits 0-9, of a stepping switch having contacts appropriate to the digits 0-9 connected to said solenoids to effect operation thereof selectively, means for advancing the stepping switch differentially under control of the calculator in accordance with the number of subtraction cycles utilized by the calculator to compute each quotient digit, means controlled by the calculator for blocking energization of said solenoids during the said subtraction cycles, and means controlled by the calculator for homing the stepping switch preparatory to the computation of each quotient digit.

6. The combination according to claim 5 wherein the stepping switch is advanced one step for each subtraction cycle and is arranged to home to the contacts thereof appropriate to the digit 9 to compensate for advances thereof in response to overdraft producing subtraction cycles.

7. The combination according to claim 6 wherein the means for advancing the stepping switch include a stepping solenoid, an energization circuit for said solenoid and a pair of normally open contacts in said circuit closed under control of the calculator in conjunction with each subtraction cycle of the latter.

8. The combination according to claim 7 wherein the record control solenoids are provided with a common energization circuit wherein the means for blocking energization thereof include a pair of contacts held open under control of the calculator all during subtraction cycles thereof.

9. The combination according to claim 8 wherein the means for homing the stepping switch include a second energization circuit for the stepping solenoid comprising a second group of stepping switch contacts appropriate to the digits -8 connected in common, an interrupter contact for the stepping solenoid, and means for maintaining the second energization circuit open all during subtraction cycles of the calculator and during energization of the record control solenoids.

10. The combination according to claim 9 wherein the means for maintaining the second energization circuit open include a first pair of contacts, a second pair of contacts, a relay energized on homing of the stepping switch and deenergized on energization of the record control solenoids, said first pair of contacts being held open bysaid relay while the same is energized, and means under control of the calculator for maintaining said second pair of contacts closed except during energization of the record control solenoids.

11. The combination according to claim 10 including a holding circuit for the relay and an energizing circuit for therelay comprising another stepping switch contact appropriate to the digit 9 and said second pair of contacts.

12. The combination according to claim 11 and including a source of electrical power for all of the said energization circuits and switching means under control of the operator of the calculator for disconnecting the source of power from the energization circuit.

13. The combination according to claim 12 including switching means under control of the calculator for disconnecting the source of power from the energization circuits except during division operations.

14. The combination according to claim 13 including another solenoid for effecting a desired recorder operation preparatory to each quotient digit recording operation, and an energization circuit for said solenoid comprising a pair of normally open contacts, a relay for closing said contacts, and switching means operated in conjunction with the calculator controlled switching means for disconnecting the source of power from the energization circuits, to connect said source of power with said relay to energize the latter, and a condenser in the last said connection to elfect deenergization of the relay when it becomes charged.

15. The combination of a calculator adapted to perform division by means of repeated subtraction, a stepping switch having a set of contacts appropriate to the digits 09, a stepping solenoid for advancing said stepping switch, an energization circuit for said solenoid, a pair of normally open contacts in said energization circuit closed under control of the calculator in conjunction with each said subtraction utilized to compute each quotient digit, means connected to the stepping switch contacts to be selectively controlled thereby, an operating circuit for said means selectively controlled by the stepping switch contacts, including said contacts, a source of power, a switch controlled by the calculator to connect said operating circuit to said source of power after all of the subtractions required in computing each quotient digit have been completed, and a second energization circuit for said stepping solenoid for homing said stepping switch, comprising a second set of stepping switch contacts appropriate to the digits 0-8 connected in common, an interrupter contact for said stepping solenoid and means for maintaining said second energization circuit abeyant all during said subtractions and during operation of said selectively controlled means, wherein said stepping switch is advanced one step for each subtraction and is arranged to home to the contacts of said stepping switch appropriate to the digit 9 preparatory to the computation of each quotient digit to compensate for advances of said stepping switch in response to overdraft producing subtractions.

16. The combination according to claim 15 wherein the means for maintaining the second energization circuit abeyant include a first pair of contacts, a second pair of contacts, a relay energized on homing of the stepping switch and deenergized on operation of the selectively controlled means, said first pair of contacts being held open by said relay while the same is energized, and means under control of the calculator for maintaining said second pair of contacts closed except during operation of said selectively controlled means.

17. The combination according to claim 16 including a holding circuit for the relay and an energizing circuit for the relay comprising another stepping switch contact appropriate to the digit 9 and said second pair of contacts.

References Cited in the file of this patent UNITED STATES PATENTS 2,093,529 Tauschek Sept. 21, 1937 2,209,434 Umhauer July 30, 1940 2,255,622 Landsiedel Sept. 9, 1941 2,531,207 Gang Nov. 21, 1950 2,633,222 Wittenmyer Mar. 31, 1953 2,675,961 Larsen Apr. 20, 1954 

